Cap device

ABSTRACT

A cap device or fuel cap has a cap main body, a cover, and a torque plate that transmits a rotational torque. The torque plate is attached to the cap main body in a rotatable manner through engagement of catching claws formed on the outer circumference of the torque plate with catching projections formed on the cap main body. The cover is held on the torque plate in a rotatable manner through engagement of engagement projections formed on the inner wall of the cover with catching claws formed on respective fixation elements. The engagement projections are arranged about an axis of the cap main body and outside the catching claws. The engagement projections are thus readily released from engagement with the catching claws under application of an external force in any of diverse directions, for example, due to a collision of a vehicle, so as to maintain the sufficient sealing properties of the cap main body.

This application claims the benefit of and priority from JapaneseApplication No. 2003-314149 filed Sep. 5, 2003, and Japanese ApplicationNo. 2003-327417 filed Sep. 19, 2003, the contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cap device that is detachablyattached to a tank opening.

2. Description of the Related Art

A cap device has, for example, a known structure shown in FIG. 28 (seeNo. JP 10-329861A). FIG. 28 is a partly sectional, side view showing aprior art fuel cap 200 for a fuel tank of an automobile. The fuel cap200 has a cap main body 202 and a cover 210 attached to an upper flange204 of the cap main body 202. The flange 204 has an outer ring element206 to hold the cover 210, and a joint element 208 that connects theouter ring element 206 with a lower portion of the cap main body 202.The joint element 208 has a fragile part with notches 209. The fragilepart is a starting point of breakage of the joint element 208 underapplication of an external force in any of diverse directions to theflange 204 via the cover 210. In the case of application of an extremelylarge external force to the periphery of the fuel cap 200, for example,in the event of a collision of the automobile, the fragile part of thejoint element 208 is broken to maintain the sufficient sealingproperties of the cap device and effectively seal the fuel tank from theatmosphere.

Such breakage is, however, not restricted in the event of the collisionof the automobile. Some inadvertent use of the fuel cap 200, forexample, an accidental drop of the fuel cap 200 during fuel supply orlocalized application of a large static load to the lower end of thecover 210, also causes breakage of the fragile part to significantlydamage the cap device 200. The breaking load at the fragile part dependsupon the direction and the depth of the notches formed in the flange204. Accurate design of the fragile part to attain breakage underapplication of loading in a predetermined range is rather difficult,since the flange 204 has a narrow width and only limited design freedom.

SUMMARY OF THE INVENTION

The object of the invention is to eliminate the drawbacks of the priorart and to provide a cap device of simple structure that does not damageits functions even in the event of an accidental drop of the cap deviceand maintains the sufficient sealing properties even under loading of anexternal force.

In order to attain at least part of the above and the other relatedobjects, the present invention is directed to a cap device that opensand closes a tank opening. The cap device includes: a closer that closesthe tank opening; a handle mechanism that rotates the closer about arotation axis of the closer; a circular plate member that is interposedbetween the closer and the handle mechanism; a plate attachmentmechanism that attaches the circular plate member to the closer in arotatable manner, while causing part of the circular plate member to beelastically deformed by an external force applied to the handlemechanism and thereby detaching the circular plate member from thecloser; and a handle mechanism attachment mechanism that holds thehandle mechanism on an outer circumference of the circular plate memberin a freely rotatable manner. The handle mechanism attachment mechanismis arranged about the rotation axis of the closer and outside the plateattachment mechanism.

In the cap device of the invention, the closer is inserted into the tankopening, and the handle mechanism then rotates to make the closer openand close the tank opening. The circular plate member is located betweenthe closer and the handle mechanism and is attached to the closer bymeans of the plate attachment mechanism. The plate attachment mechanismelastically deforms part of the circular plate member or the closer todetach the circular plate member from the closer.

The plate attachment mechanism readily sets the loading required fordetachment of the circular plate member from the closer by simplychanging the shape, the number, and the mechanical strength of theelastically deformable part of the circular plate member or the closer.The plate attachment mechanism thus readily sets the breaking load inany of diverse directions of an external force without restriction ofthe sealing structure of the closer.

The cap device of the invention has the handle mechanism attachmentmechanism that holds the handle mechanism on the outer circumference ofthe circular plate member in a freely rotatable manner. The handlemechanism attachment mechanism causes part of the handle mechanism orthe circular plate member to be elastically deformed and thereby easilydetaches the handle mechanism from the circular plate member. The handlemechanism attachment mechanism is arranged about the rotation axis ofthe closer and outside the plate attachment mechanism. The handlemechanism attachment mechanism produces a moment as a force of detachingthe circular plate member from the closer under application of a lateralexternal force to the handle mechanism, thus enabling the circular platemember to be readily detached from the closer.

When a large external force is applied to the cap device to detach thehandle mechanism from the circular plate member, for example, due to anaccidental drop of the cap device during fuel supply, elasticdeformation of the handle mechanism attachment mechanism enables theseparate handle mechanism to be attached again to the circular platemember. The cap device of this structure is not significantly damaged inthe event of an accidental drop, unlike the prior art cap that is brokenat the fragile part.

In one preferable embodiment of the cap device of the invention, thecircular plate member is a torque plate that transmits a rotationaltorque, which is applied to the handle mechanism in either of a closingdirection and an opening direction, to the closer to an extent of notexceeding a preset level.

In this preferable embodiment, the plate attachment mechanism may havean elastically deformable catching claw that is formed on an outercircumference of the torque plate, and a catching projection that isformed on an outer circumference of the closer to engage with thecatching claw. The handle mechanism may include a handle, and a coverthat holds the handle and surrounds an upper portion and the outercircumference of the torque plate. The handle mechanism attachmentmechanism may have an engagement projection that is formed on an innerwall of the cover, and a catching recess that is formed on the outercircumference of the torque plate to receive the engagement projectionfit therein.

These and other objects, features, aspects, and advantages of thepresent invention will become more apparent from the following detaileddescription of the preferred embodiments with the accompanied drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a half sectional view showing a fuel cap in one embodiment ofthe invention;

FIG. 2 shows the fuel cap that is screwed to a filler neck to close ainlet opening;

FIG. 3 is a perspective view showing the fuel cap detached from thefiller neck;

FIG. 4 is an enlarged sectional view showing a gasket attached to a sealsupport element of the fuel cap;

FIG. 5 illustrates the shape of the gasket;

FIG. 6(A) shows a series of compression of the gasket as the fuel cap isclosed;

FIG. 6(B) shows the series of the compression of the gasket after thestate of FIG. 6(A);

FIG. 6(C) shows the series of the compression of the gasket after thestate of FIG. 6(B);

FIG. 6(D) shows the series of the compression of the gasket after thestate of FIG. 6(C);

FIG. 7 is a graph showing variations in reactive force against theflexure length of the gasket;

FIG. 8 is a graph showing variations in sealing face pressure againstthe flexure length of the gasket;

FIG. 9 is a graph showing variations in sealing face pressure byreactive force against the flexure length of the gasket;

FIG. 10 is a decomposed perspective view showing a torque mechanismlocated on a cover and an upper portion of a cap main body;

FIG. 11 is a top view of the torque mechanism;

FIG. 12 is a perspective view showing a main part of the torquemechanism;

FIG. 13 is a sectional view showing the side of the fuel cap;

FIG. 14 shows the periphery of a torque plate in the torque mechanism;

FIG. 15 shows the functions of first springs and second springs;

FIG. 16 shows a series of operations of the torque mechanism;

FIG. 17 shows the series of operations of the torque mechanism after thestate of FIG. 16;

FIG. 18 shows the series of operations of the torque mechanism after thestate of FIG. 17;

FIG. 19 shows the series of operations of the torque mechanism after thestate of FIG. 18;

FIG. 20 shows the series of operations of the torque mechanism after thestate of FIG. 19;

FIG. 21 shows the series of operations of the torque mechanism after thestate of FIG. 20;

FIG. 22 shows the series of operations of the torque mechanism after thestate of FIG. 21;

FIG. 23 is a graph showing a variation in rotational torque against therotational angle of a grip member;

FIG. 24 is a sectional view showing a gasket in one modified example;

FIG. 25 is a sectional view showing a gasket in another modifiedexample;

FIG. 26 is a sectional view showing a gasket in still another modifiedexample; and

FIG. 27 is a sectional view showing a gasket in another modifiedexample.

FIG. 28 is a partly sectional, side view showing a related art fuel capfor a fuel tank of an automobile.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some modes of carrying out the invention are discussed below aspreferred embodiments.

(1) General Structure of Fuel Cap 10

FIG. 1 is a half sectional view showing a fuel cap 10 (cap device) inone embodiment of the invention. The fuel cap 10 is attached to a fillerneck FN having an inlet opening FNb (tank opening) to feed a supply offuel to a fuel tank (not shown). The fuel cap 10 has a cap main body 20(closer) that is made of a synthetic resin material like polyacetal, acover 40 that is mounted on the cap main body 20 and has a handle thecover 40 made of a synthetic resin material like nylon, an inner cover30 that closes an upper opening of the cap main body 20 and defines avalve chest 25, a pressure regulating valve 50 that is received in thevalve chest 25, a torque mechanism 80, and a ring-shaped gasket GS thatis attached to the upper outer circumference of the cap main body 20 toseal the cap main body 20 from the filler neck FN.

(2) Construction of Constituents of Fuel Cap 10

The construction of the respective constituents of the fuel cap 10 inthe embodiment is discussed below in detail.

(2)-1 Cap Main Body 20

The cap main body 20 has a substantially cylindrical outer tubular body20 a with a male threading element 21 (second threading element), whichengages with a female threading element FNc (first threading element)formed on the inner wall of the pipe-shaped filler neck FN(opening-formation member), and a valve chest-formation body 20 b thatis located in the lower portion of the inside of the outer tubular body20 a. The valve chest-formation body 20 b receives a positive pressurevalve and a negative pressure valve functioning as the pressureregulating valve 50 therein. The inner cover 30 is pressed into theupper portion of the valve chest-formation body 20 b to cover over thevalve chest 25.

The gasket GS is set on a lower face of an upper flange 22 of the capmain body 20. The gasket GS is located between a seal support element 24of the flange 22 and the inlet opening FNb of the filler neck FN. Whenthe fuel cap 10 is inserted into the inlet opening FNb, the gasket GS ispressed against the seal support element 24 to exert the sealingeffects. The seal support element 24 has a curved face to hold thegasket GS.

FIG. 2 shows the fuel cap 10 that is screwed to the filler neck FN toclose the inlet opening FNb. FIG. 3 is a perspective view showing thefuel cap 10 detached from the filler neck FN. With referring to FIGS. 2and 3, a screw mechanism is formed on the inner circumferential wall ofthe filler neck FN and the outer circumference of the outer tubular body20 a of the cap main body 20. The screw mechanism functions to screw thefuel cap 10 to the filler neck FN, and includes the female threadingelement FNc (first threading element) formed on the inner wall of thefiller neck FN and the male threading element 21 (second threadingelement) formed on the lower portion of the outer circumference of theouter tubular body 20 a. The female threading element FNc is threadingprojections from a leader FNc1 close to the inlet opening FNb toward thedepth of the fuel tank. The male threading element 21 has a thread ridge21 a and a thread groove 21 b. The lower end of the thread ridge 21 a isa leader 21 c that engages with the leader FNc1 of the female threadingelement FNc (see FIG. 2). A stopper 21 d is formed upright to cross thethread groove 21 b. The stopper 21 d is located at a position of about200 degrees from the leader 21 c of the male threading element 21. Whenthe fuel cap 10 is inserted into the inlet opening FNb, the stopper 21 dcomes into contact with the leader FNc1 of the female threading elementFNc to restrict further rotation of the fuel cap 10 in its closingdirection. The female threading element FNc has a screw thread pitch of6.35 mm per rotation.

When the fuel cap 10 fit in the inlet opening FNb is rotated in itsclosing direction, the male threading element 21 is screwed in thefemale threading element FNc. When the gasket GS is compressed in theaxial direction to or over a preset displacement, the stopper 21 d comesinto contact with the leader FNc1 of the female threading element FNc torestrict further rotation. The fuel cap 10 is fastened to the fillerneck FN in this state.

(2)-2 Gasket

(2)-2-1 Structure of Gasket GS

FIG. 4 is an enlarged sectional view showing the gasket GS attached tothe seal support element 24 of the fuel cap 10. The gasket GS has agasket main body GSa that is formed in a substantially V shape and iscompressed to shorten the length in its bending direction. The gasketmain body GSa has a substantially U-shaped slit GSb open to the outercircumference.

Multiple sealing projections GSc are protruded from the outercircumference of the gasket main body GSa. The multiple sealingprojections GSc include a first pipe sealing projection GSd1 and asecond pipe sealing projection GSd2, which come into contact with a pipesealing face FNf, and a first body sealing projection GSe1 and a secondbody sealing projection GSe2, which come into contact with the sealsupport element 24.

The first pipe sealing projection GSd1 is formed on an opening end ofthe slit GSb and is protruded to be pressed against the pipe sealingface FNf in an initial stage of a closing operation. The second pipesealing projection GSd2 is protruded to have a greater sealing facepressure than the first pipe sealing projection GSd1 and to be pressedagainst the pipe sealing face FNf after the initial stage of the closingoperation.

FIG. 5 illustrates the shape of the gasket GS. As illustrated in FIG. 5,the first body sealing projection GSe1 and the second body sealingprojection GSe2 are positioned to have practically equal angles α and βin a range of 30 to 45 degrees to the first pipe sealing projection GSd1and to the second pipe sealing projection GSd2 in a non-compressed stateof the gasket GS. The first body sealing projection GSe1 and the secondbody sealing projection GSe2 are positioned to produce a maximum stressto a reactive force produced when the first pipe sealing projection GSd1and the second pipe sealing projection GSd2 are pressed against the pipesealing face FNf.

The gasket main body GSa has thin wall sections GSf between theadjoining sealing projections GSc to define hollow elements from theseal support element 24. The hollow elements defined by the thin wallsections GSf reduce the total cross section of the gasket GS to 30 to50% or preferably 35 to 45% of the area of an imaginary circle CL goingthrough the apexes of the sealing projections GSc.

The sealing projections GSc preferably have a curvature R of not lessthan 0.5 mm. This curvature facilitates cleaning of recesses in aninjection mold for the gasket GS with the sealing projections GSc andenhances the productivity.

(2)-2-2 Functions of Gasket GS

FIG. 6 shows compression of the gasket GS as the fuel cap 10 is closed.In the initial stage of the closing operation of the fuel cap 10, thefirst pipe sealing projection GSd1 of the gasket GS comes into contactwith the pipe sealing face FNf (FIG. 6(A)). The further closingoperation causes the gasket GS to be compressed in the bending directionand narrow the opening of the slit GSb (FIG. 6(B)). In the next stage,the second pipe sealing projection GSd2 comes into contact with the pipesealing face FNf (FIG. 6(C)). In the last stage, the second pipe sealingprojection GSd2 is pressed against the pipe sealing face FNf, so thatthe fuel cap 10 closes the inlet opening FNb (FIG. 6(D)). Namely thefirst pipe sealing projection GSd1 mainly exerts the sealing effects inthe initial stage of the closing operation. The second pipe sealingprojection GSd2 exerts the sealing effects in the closed state of thefuel cap 10.

FIG. 7 is a graph showing variations in reactive force against theflexure length of the gasket. The solid-line curve regards the gasket GSof the embodiment and the dotted-line curve regards a prior art C-shapedgasket. Here the flexure length represents a compressed length(compression degree) of the gasket in its bending direction. Therelation between the flexure length and the rotational angle of the fuelcap depends upon various parameters like the hardness and the shape ofthe gasket. In an example where a 360-degree rotation of a fuel capgives a flexure length of 6.3 mm, the fuel cap closed at an angle of 198degrees gives a flexure length of 3.6 mm. The fuel cap rotated from itsfull close position in its opening direction by 90 degrees gives aflexure length of 1.6 mm.

The closing operation of the fuel cap bends the gasket and increases thereactive force of the gasket. The reactive force of greater than 160 Nproduced in the closing operation of the fuel cap deteriorates theoperating characteristics of the fuel cap. The reactive force is thuspreferably not greater than 160 N or more preferably not greater than130 N. The prior art gasket gives only a flexure length of about 1.5 mmat the reactive force of 160 N and has an abrupt increase in reactiveforce to deteriorate the operating characteristics. The gasket GS of theembodiment, on the other hand, gives a flexure length of at least 3.6 mmin the full close position and does not have any abrupt increase inreactive force to ensure the good operating characteristics.

FIG. 8 is a graph showing variations in sealing face pressure againstthe flexure length of the gasket. The solid-line curve regards thegasket GS of the embodiment and the dotted-line curve regards the priorart C-shaped gasket. Here the sealing face pressure represents apressure of the gasket against the pipe sealing face FNf. As the fuelcap 10 is closed, the sealing face pressure increases with an increasein flexure length of the gasket GS. In the initial stage of the closingoperation having the flexure length of 0.5 to 1.3 mm, the first pipesealing projection GSd1 mainly contributes to the increase in sealingface pressure. With an increase in closing angle of the fuel cap 10 tomake the flexure length of the gasket GS exceed 1.3 mm, the place of thelarge sealing face pressure shifts from the first pipe sealingprojection GSd1 to the second pipe sealing projection GSd2. As shown inFIGS. 7 and 8, the gasket GS of the embodiment ensures the greatersealing face pressure with the smaller reactive force, compared with theprior art C-shaped gasket.

In order to ensure the sealing face pressure of at least a preset levelagainst the flexure length of the gasket GS and prevent an excessivestress from being applied to the gasket GS, the stopper 21 d (see FIG.2) defines the full closing depth to be not less than 2 mm or preferablyto be in a range of 3 to 5 mm.

FIG. 9 is a graph showing variations in sealing face pressure byreactive force against the flexure length of the gasket. The solid-linecurve regards the gasket GS of the embodiment and the dotted-line curveregards the prior art C-shaped gasket. As clearly understood from thegraph of FIG. 9, the gasket GS of the embodiment has the greater sealingface pressure per unit reactive force against the same flexure length,compared with the prior art C-shaped gasket.

(2)-2-3 Effects of Gasket GS

1. The gasket GS of the embodiment gives a greater sealing face pressurewith a smaller closing force and ensures the good operatingcharacteristics.

2. As shown in FIG. 5, the spaces defined by the thin wall sections GSfof the gasket GS reduce the total cross section of the gasket GS to 30to 50% or preferably 35 to 45% of the area of the imaginary circle CLgoing through the apexes of the sealing projections GSc. The presence ofthe thin wall sections GSf desirably decreases the required quantity ofthe material, while ensuring the high sealing face pressure of thegasket GS. The gasket GS can thus be made of a rubber material havingexcellent fuel permeation resistance, for example, expensivefluororubber, without increasing the manufacturing cost. Thefluororubber exerts the excellent fuel permeation resistance even whenan alcohol of a small molecular weight is applied to the fuel.

3. The fuel cap 10 may adopt a quick-turn structure to open and closethe inlet opening FNb by simple rotation of a preset angle, for example,180 degrees. In this structure, the cover 40 is generally required tohave a lost motion mechanism that idles in the range of a preset angle,in order to prevent a decrease in sealing face pressure of the gasketdue to an external force applied to the cover 40. The gasket GS of theembodiment, however, ensures the high sealing properties even when thecover 40 receives an external force and rotates in its opening directionby approximately 90 degrees in to decrease the flexure length to about1.6 mm. The gasket GS of the embodiment thus ensures the sufficientsealing face pressure of or over a preset level without the lost motionmechanism of the complicated structure.

4. While the gasket GS is swollen with the fuel, the first body sealingprojection GSe1 and the second body sealing projection GSe2 prevent theouter face of the gasket main body GSa from coming into contact with theseal support element 24. This structure effectively prevents an increasein rotational torque with an increase in contact area.

5. The fuel cap 10 of the embodiment has the large screw thread pitch tomove the cap main body 20 by at least 3 mm in the axial direction with arotation of 180 degrees. This structure enables the fuel cap 10 to beopened and closed by rotation of a small angle and thus ensures the goodoperating characteristics.

6. The gasket GS of the embodiment is designed to hold the sealing facepressure of at least 0.3 MPa when the cap main body 20 is rotated by 90degrees in its opening direction from the full close position. Thegasket GS desirably ensures the sufficient sealing properties even whenthe cap main body 20 is rotated by approximately 90 degrees in itsopening direction from the full close position due to an external force.

(2)-3 Structure of Cover 40

Referring back to FIG. 1, the cover 40 functions as a manipulatingmechanism and is attached to the flange 22 via the torque mechanism 80in a rotatable and freely detachable manner. The cover 40 includes anupper wall 41, a handle 42 mounted on the upper wall 41, and a side wall43 formed around the upper wall 41 and is integrally made of aconductive resin by injection molding. Engagement projections 43 a areprotruded inward from the side wall 43 to be arranged at equal intervalsalong the circumference. The engagement projections 43 a function to fixthe cover 40 to the cap main body 20 via the torque mechanism 80. Theattachment structure of the cover 40 is discussed below.

(2)-4 Construction of Torque Mechanism 80

(2)-4-1 General Structure of Torque Mechanism 80

FIG. 10 is a decomposed perspective view showing the torque mechanism 80located on the cover 40 and the upper portion of the cap main body 20.FIG. 11 is a top view of the torque mechanism 80. The torque mechanism80 clicks when the cover 40 receives a rotational torque of or over apreset level in the closing operation of the fuel cap 10 in the inletopening FNb. The user can thus confirm that the fuel cap 10 is attachedto the filler neck FN with a rotational torque of or over the presetlevel.

As shown in FIGS. 10 and 11, the torque mechanism 80 includes two bodyengagement elements 23 arranged along the circumference of the outertubular body 20 a, cover engagement elements 46 and guide elements 48that are protruded from the bottom face of the upper wall 41 of thecover 40, and a torque plate 90.

(2)-4-2 Structure of Body Engagement Element 23

The body engagement elements 23 are arranged on the circumference of theouter tubular body 20 a to catch the torque plate 90 for transmission ofa rotational torque. Each of the body engagement elements 23 has a firstlocking end 23 a, a second locking end 23 b, and a ridge-like engagementprojection 23 c (first engagement element) protruded between the firstlocking end 23 a and the second locking end 23 b. The body engagementelement 23 also has a first guide end 23 d, a second guide end 23 e, anda guide step 23 f formed between the first guide end 23 d and the secondguide end 23 e.

(2)-4-3 Structure of Cover 40

The two cover engagement elements 46 are protruded from the bottom faceof the upper wall 41 of the cover 40 to be arranged along thecircumference of the cover 40. Each of the cover engagement elements 46of the cover 40 is a cylindrical projection to catch the torque plate 90for transmission of a rotational torque. Each of the guide elements 48has a peripheral guide wall 48 a, a first guide groove 48 b, and asecond guide groove 48 c. The first guide groove 48 b is formed on thecircumference around the rotational axis, while the second guide groove48 c is formed to be coupled with the first guide groove 48 b and to beinclined relative to the axial center. A guide locking upright wall 48 dis formed on the end of the first guide groove 48 b and on the end ofthe peripheral guide wall 48 a to face the first guide groove 48 b.

(2)-4-4 Structure of Torque Plate 90

The torque plate 90 has a disc-shaped torque body 91 made of a resin.The torque body 91 includes a disc-shaped arm support 91 a, an outerring 91 b surrounding the arm support 91 a, and a linkage element 91 clinking the arm support 91 a with the outer ring 91 b. Guide grooves,torque arms, and spring elements are formed on the torque body 91.Torque arms 93 (second engagement elements) are formed on the armsupport 91 a. Each of the torque arms 93 includes an arm body 93 aprotruded from the arm support 91 a, a torque engagement projection 93 cprotruded from the outer circumference of the arm body 93 a, and a guideprojection 93 f protruded upward from a free end 93 d of the arm body 93a. The torque arm 93 is a cantilever with a support base 93 b as thefulcrum and has the free end 93 d apart from the torque body 91 by acertain distance.

With a rotation of the cover 40 in the closing direction (clockwise),the torque engagement projection 93 c is pressed against the engagementprojection 23 c of the body engagement element 23. The dual support ofthe support base 93 b and the free end 93 d bends the torque arm 93 inthe direction perpendicular to its longitudinal axis and causes thetorque engagement projection 93 c of the torque arm 93 to ride over theengagement projection 23 c of the body engagement element 23 (see FIG.19).

(2)-4-5 Attachment Structure of Torque Plate 90 and Cover 40

The following describes the attachment structure (plate attachmentmechanism) of the cap main body 20 and the torque plate 90 and theattachment structure (grip attachment mechanism) of the torque plate 90and the cover 40. FIG. 12 is a perspective view showing a main part ofthe torque mechanism 80. FIG. 13 is a sectional view showing the side ofthe fuel cap 10. Catching claws 98 a of plate engagement elements 98 areformed is along the inner circumference of the outer ring 91 b of thetorque plate 90. The catching claws 98 a are protruded from the innerwall of the outer ring 91 b toward the center axis and are formed to beobservable from the top through notches 98 b and elastically deformablein the axial direction. Arc-shaped catching projections 22 b are formedon the outer circumference of the flange 22 of the cap main body 20. Thetorque plate 90 is attached to the cap main body 20 in a rotatablemanner through engagement of the catching claws 98 a with the catchingprojections 22 b.

Fixation elements 99 are arranged on the outer circumference of theouter ring 91 b of the torque plate 90. Each of the fixation elements 99has a catching recess 99 b to form a catching claw 99 a. The engagementprojections 43 a formed inward on the side wall 43 of the cover 40 arefit in the catching recesses 99 b of the mating fixation elements 99, sothat the torque plate 90 supports the cover 40 in a rotatable manner(approximately 20 degrees). The fixation positions of the engagementprojections 43 a with the catching recesses 99 b of the fixationelements 99 is located above the fixation positions of the catchingclaws 98 a of the plate engagement elements 98 with the catchingprojections 22 b of the flange 22.

The torque plate 90 is attached to the cap main body 20 throughengagement of catching claws 98 a of the plate engagement elements 98 ofthe torque plate 90 with the catching projections 22 b of the flange 22of the cap main body 20. The cover 40 is then attached to the torqueplate 90 through engagement of the engagement projections 43 a of thecover 40 with the catching claws 99 a of the torque plate 90. Thisassembles the cap main body 20, the torque plate 90, and the cover 40 tothe fuel cap 10.

As shown in FIG. 10, fragile grooves 95 a as part of fragile elements 95are formed along the inner circumference of the outer ring 91 b of thetorque plate 90. The fragile grooves 95 a are located to link thenotches 98 b in the circumferential direction.

When large external forces F1 and F2 are applied to the cover 40 asshown in FIG. 13, for example, at the time of a collision of a vehicle,the fragile elements 95 supporting the cover 40 may be broken along thecircumference of the torque plate 90. Otherwise the catching claws 98 aof the plate engagement elements 98 may be detached from the catchingprojections 22 b of the flange 22, or the engagement projections 43 a ofthe cover 40 may be detached from the fixation elements 99. In any case,the seal support element 24 of the cap main body 20 for holding thegasket GS is not damaged and thus ensures the sufficiently high sealingproperties of the gasket GS. The fixation positions of the engagementprojections 43 a of the cover 40 with the catching recesses 99 b of thefixation elements 99 of the torque plate 90 is located above thefixation positions of the catching claws 98 a of the plate engagementelements 98 with the catching projections 22 b of the flange 22.Application of the upper external force F2 in addition to the externalforce F1 leads to detachment of either the cover 40 or the torque plate90. The structure of the embodiment thus ensures the high sealingproperties against diverse external forces. In the case of applicationof the external force F2 onto the cover 40, the momentum is generatedfrom the opposite fixation element 99 as the fulcrum to readily detachthe cover 40.

The plate engagement elements 98 (plate attachment mechanism) and thefixation elements 99 (grip attachment mechanism) are optimized to setthe breaking loads against the diverse external forces withoutrestriction of the shape of the seal support element 24.

(2)-4-6 Support Mechanism of Torque Plate 90

FIG. 14 shows the periphery of the torque plate 90. As shown in FIGS. 10and 14, the torque plate 90 has first springs 96 and second springs 97to hold the torque plate 90 between the bottom face of the upper wall 41of the cover 40 and the upper portion of the cap main body 20. The fourfirst springs 96 are arranged at angles of 90 degrees in thecircumferential direction on the center portion of the torque plate 90.The first springs 96 apply a vertical spring force to the bottom face ofthe upper wall 41 of the cover 40. As shown in FIG. 15, each of thefirst springs 96 has an arm 96 a that is formed on the same plane as thetop face of the torque plate 90 and is extended as a cantilever in thecircumferential direction, and a pressure projection 96 b that is formedon a free end of the arm 96 a to be protruded upward from the top faceof the torque plate 90. Each of the second springs 97 has an arm body 97a that is formed as a cantilever slightly inclined downward, and apressure projection 97 b that is formed on a free end of the arm body 97a to be pressed against an inclined plane 22 a of the flange 22. One endof the second spring 97 is tilted in a notch 97 c formed on the top faceof the torque plate 90. The pressure projections 97 b of the secondsprings 97 press the inclined plane 22 a of the flange 22, so that thesecond springs 97 are positioned in both the vertical direction and inthe radial direction.

(3) Opening and Closing Operations of Fuel Cap 10

The following describes the functions of the torque mechanism 80 whenthe inlet opening FNb of the filler neck FN is opened and closed by thefuel cap 10. FIGS. 16 through 20 show a closing operation of the fuelcap 10. FIGS. 20 through 22 show an opening operation of the fuel cap10. The torque mechanism 80 has two cover engagement elements 46, 46,two guide elements 48, 48, two torque arms 93, 93, and two bodyengagement elements 23, 23 arranged about the rotational axis of thetorque plate 90, as mentioned above. The torque mechanism 80 accordinglyhas the symmetrical operations.

(3)-1 Closing Operation of Fuel Cap 10

The user holds the handle 42 of the cover 40 with thumb and index fingerand inserts the cap main body 20 in the axial direction into the inletopening FNb. The leader 21 c of the male threading element 21 is set onthe leader FNc1 of the female threading element FNc (see FIG. 2). Whenthe user applies a rotational force to the handle 42 in the closingdirection (clockwise), the torque mechanism 80 performs a series ofoperations as shown in FIGS. 16 to 20.

When a rotational force is applied to the handle 42 in the closingdirection, the cover engagement elements 46, 46 of the cover 40 areguided by mating rib guide elements 92, while the guide projections 93 fof the torque arms 93 are guided by the mating guide elements 48, asshown in FIG. 16. The cover engagement elements 46 then come intocontact with pressure ends 92 a of the respective rib guide elements 92,while the guide projections 93 f of the torque arms 93 respectively movein the first guide grooves 48 b to come into contact with the guidelocking upright walls 48 d. In this state, the cover 40 moves togetherwith the torque plate 90 in the closing direction, and the torque arms93 are supported by both the support bases 93 b and the guideprojections 93 f.

The cover 40 and the torque plate 90 are slightly rotated as shown inFIG. 17. The torque engagement projections 93 c of the torque arms 93then engage with the engagement projections 23 c of the body engagementelements 23 by a lap Lp as shown in FIG. 18. Rotation of the handle 42by approximately 180 degrees causes the cap main body 20 to be rotatedintegrally with the cover 40 and the torque plate 90 through thisengagement. This inserts the cap main body 20 into the inlet opening FNbin the closing direction and enhances the engagement force of the malethreading element 21 with the female threading element FNc. When thereactive force produced by the increasing engagement force exceeds apreset rotational torque, the torque engagement projections 93 c of thetorque arms 93 ride over the engagement projections 23 c of the bodyengagement elements 23 to be set in a released position, as shown inFIG. 19.

With a slight rotation of the torque plate 90, the engagementprojections 23 c of the body engagement elements 23 engage with thetorque engagement projections 93 c of the torque arms 93 by the lap Lp(see FIG. 18) and press the torque engagement projections 93 c in theradial direction. The torque arms 93 supported by the two fulcrums arethus elastically deformed to be set in a released position. The torquearms 93 click when being set in the released position. The fuel cap 10is thus fit in the inlet opening FNb with some clamping torque to closesthe inlet opening FNb. In the released position of the torque arms 93,guide projections 94 move in the guide steps 23 f to come into contactwith the first guide ends 23 d as shown in FIG. 20. The cover 40, thetorque plate 90, and the cap main body 20 rotate integrally to bring thestopper 21 d of the male threading element 21 into contact with theleader FNc1 of the female threading element FNc. This prevents excessivecompression of the gasket GS.

(3)-2 Opening Operation of Fuel Cap 10

In order to open the fuel cap 10, the user holds the handle 42 of thecover 40 with thumb and index finger and applies a counterclockwiserotational force to the handle 42 in the state of FIG. 20. In thisstate, the cap main body 20 is fit in the filler neck FN. The coverengagement elements 46 of the cover 40 move in the mating rib guideelements 92 to come into contact with pressure ends 92 b, while theguide elements 48 guide the guide projections 93 f of the torque arms 93through the first guide grooves 48 b to the second guide grooves 48 cand bend the arm bodies 93 a of the torque arms 93 about the supportbases 93 b toward the center, as shown in FIG. 21. The torque engagementprojections 93 c of the torque arms 93 are thus deflected toward thecenter to be apart from the engagement positions with the engagementprojections 23 c of the body engagement elements 23. This produces a gapGp and gives no lap Lp (see FIG. 18).

As shown in FIG. 22, as the cover 40 and the torque plate 90 rotatecounterclockwise relative to the cap main body 20, the guide projections94 are guided on the guide steps 23 f to come into contact with thesecond guide ends 23 e. The torque engagement projections 93 c of thetorque arms 93 move in the deflected position not to engage with theengagement projections 23 c of the body engagement elements 23. Thetorque arms 93 accordingly do not click.

While the guide projections 94 are in contact with the second guide ends23 e, the rotational torque of the cover 40 is transmitted to the capmain body 20 via the cover engagement elements 46 of the cover 40, thepressure ends 92 b of the torque arms 93, the guide projections 94, andthe second guide ends 23 e of the body engagement elements 23. The cover40, the torque plate 90, and the cap main body 20 thus rotate integrallycounterclockwise.

Rotation of the cap main body 20 with the cover 40 by approximately 180degrees resumes the state of FIG. 16. The male threading element 21 isseparate from the leader FNc1 of the female threading element FNc of thefiller neck FN, so that the cap main body 20 is released from the fillerneck FN. The fuel cap 10 is then detached from the filler neck FN toopen the inlet opening FNb.

FIG. 23 is a graph showing a variation in rotational torque against therotational angle of the handle 42. In the initial state of the closingoperation when the fuel cap 10 is inserted into the inlet opening FNband the handle 42 is rotated in the range of 0 to 50 degrees, the malethreading element 21 does not engage with the female threading elementFNc (idling state). The gasket GS is accordingly not contact with thepipe sealing face FNf Further rotation of the handle 42 exceeding 50degrees compresses the gasket GS and increases the rotational torque.The gasket GS is gradually compressed from the state of FIG. 6(A) to thestate of FIG. 6(B) and then the state of FIG. 6(C). When the rotationalangle of the handle 42 exceeds 180 degrees, the torque mechanism 80clicks (in the state of FIG. 19). When the rotational angle of thehandle 42 reaches 200 degrees, the stopper 21 d works to stop furtherrotation of the fuel cap 10 (in the state of FIG. 20).

(4) Effects of Embodiment

The structure of the embodiment has the following effects, in additionto those discussed above.

(4)-1 In the closing operation of the fuel cap 10, the torque plate 90clicks when the torque engagement projections 93 c of the torque arms 93of the torque plate 90 ride over the engagement projections 23 c of thebody engagement elements 23. The user can thus confirm clamping of thefuel cap 10 with a certain level of torque. This structure enables thefuel cap 10 to be clamped with the certain level of torque, regardlessof the elasticity of the gasket GS.

(4)-2 In the structure of the torque mechanism 80, when the cover 40 isrotated in the opening direction to open the fuel cap 10, the torqueengagement projections 93 c of the torque arms 93 are deflected by theguide elements 48 toward the center axis not to be in contact with theengagement projections 23 c of the body engagement elements 23. Thepositional relation between the torque engagement projections 93 c andthe engagement projections 23 c thus resume the initial state withoutany contact. In this state, the rotational torque is sufficiently smalland there is no click. The user accordingly feels anything odd.

(4)-3 At a start of the closing operation of the fuel cap 10, the handle42 is located at a preset position defined by the leader FNc1 of thefemale threading element FNc as shown in FIG. 16. At a start of theopening operation of the fuel cap 10, the handle 42 is located atanother preset position defined by the stopper 21 d of the malethreading element 21 in contact with the leader FNc1 of the femalethreading element FNc as shown in FIG. 20. This ensures the goodoperating characteristics. Simple integral formation of the stopper 21 dwith the male threading element 21 makes the fuel cap 10 applicable tothe filler neck FN with the conventional female threading element FNc.This does not cause a significant cost increase.

(4)-4 The maximum rotational angle of the fuel cap 10 in the closingdirection is 160 to 200 degrees. Namely the fuel cap 10 is fully closedby approximately half a turn of the handle 42. This structure does notrequire plural turns of the handle 42 and thus ensures the goodoperating characteristics.

(5) Modifications

The embodiment discussed above is to be considered in all aspects asillustrative and not restrictive. There may be many modifications,changes, and alterations without departing from the scope or spirit ofthe main characteristics of the present invention. Some examples ofpossible modification are given below.

(5)-1 The above embodiment regards the structure of the fuel cap usedfor the fuel tank of the automobile. The structure of the invention maybe applied to another cap, for example, a cap for a radiator tank.

(5)-2 The structure of the gasket is not restricted to the aboveembodiment, but the gasket may have any of other cross sections shown inFIGS. 24 through 27. A gasket GS-B shown in FIG. 24 has a slit GSb-Bopen slightly upward. A gasket GS-C shown in FIG. 25 has a slit GSb-Copen downward. This structure effectively prevents an undercut of theslit GSb-C and facilitates release of the gasket GS-C from a mold. Agasket GS-D shown in FIG. 26 is formed in a C shape and has a slit GSb-Dthat extends from a center circle to the outside. A gasket GS-E shown inFIG. 27 is formed in an elliptic shape and has a V-shaped slit GSb-E.

(5)-3 In the above embodiment, the fuel cap 10 applies the torsionalforce to the gasket GS in its rotation. The fuel cap may be closed by avertical operational force, as long as the force is applied in thebending direction (in the direction of the rotational axis).

(5)-4 The tank with the gasket is not restricted to the fuel tank butmay be any tank for storing another fluid.

(5)-5 The material of the gasket is not restricted to the fluororubber,but the gasket may be made of another material, for example, elastomerlike NBR-PVC.

(5)-6 In the structure of the embodiment, when the fuel cap 10 isrotated in the closing direction, the torque engagement projections 93 cengage with the engagement projections 23 c by the lap Lp as shown inFIG. 18. When the fuel cap 10 is rotated in the opening direction, onthe other hand, the torque arms 93 are deflected to produce a gap Gp andno lap Lp as shown in FIG. 21. The lap Lp may not be equal to zero butmay be reduced to a level that does not make the user feel odd.

(5)-7 In the embodiment discussed above, the stopper is applied to thequick-turn constant torque cap. The stopper may be applied to theconventional screw cap or constant displacement cap. The constantdisplacement cap ensures the sealing properties of or over a certainlevel by the stroke (displacement) in the axial direction, instead ofthe torque. The use of the stopper effectively notifies the user of fullclose of the cap.

All changes within the meaning and range of equivalency of the claimsare intended to be embraced therein. The scope and spirit of the presentinvention are indicated by the appended claims, rather than by theforegoing description.

1. A cap device that opens and closes a tank opening, the cap devicecomprising: a closer that closes the tank opening; a handle mechanismthat rotates the closer about a rotation axis of the closer and includesa handle and a cover that holds the handle; a torque plate interposedbetween the closer and the handle mechanism, the torque platetransmitting a rotational torque applied to the handle mechanism in aclosing direction and an opening direction to the closer within a presetlevel; a plate attachment mechanism that attaches the torque plate tothe closer, the plate attachment mechanism being configured such thatparts of the torque plate are elastically deformed by an external forceapplied to the handle mechanism and thereby detaching the torque platefrom the closer; and a handle mechanism attachment mechanism that holdsthe handle mechanism on an outer circumference of the torque plate in arotatable manner, wherein the handle mechanism attachment mechanism isarranged about the rotation axis of the closer and outside the plateattachment mechanism, wherein the torque plate has first springs andsecond springs that hold the torque plate between an upper wall of thecover and an upper portion of the closer, wherein the first springs andthe second springs include an arm formed as a cantilever that iselastically deformed in an axial direction of the closer, wherein thetorque plate has a fragile element formed along an inner circumferenceof the torque plate, and wherein the fragile element includes fragilegrooves on the torque plate.
 2. The cap device in accordance with claim1, wherein the plate attachment mechanism has an elastically deformablecatching claw that is formed on an outer circumference of the torqueplate, and a catching projection that is formed on an outercircumference of the closer to engage with the catching claw.
 3. The capdevice in accordance with claim 2, wherein the handle mechanism includesa handle and a cover that holds the handle and surrounds an upperportion and the outer circumference of the torque plate, and the handlemechanism attachment mechanism includes an engagement projection that isformed on an inner wall of the cover, and a catching recess that isformed on the outer circumference of the torque plate to engage with theengagement projection.